1. Field of the Invention
The present invention relates generally to an internal combustion engine having a combustion heater and, more particularly, to an internal combustion engine having a combustion heater for introducing a combustion gas into an intake system of the internal combustion engine in order to speed up warm-up of the internal combustion engine.
2. Related Background Art
An internal combustion engine mounted in a vehicle such as an automobile, etc. is constructed to operate at a high efficiency within a predetermined temperature range. The reason is that an engine fuel such as gasoline, a light oil, etc. is hard to evaporate at, e.g., a low temperature with the result that there arise troubles such as a starting characteristic is impaired and so on, because of the difficulty of igniting those fuels, and hence those troubles should be prevented.
Further, as known well, an interior of a car room can be warmed by utilizing the heat evolved in the internal combustion engine when the engine works, but can not be warmed if a heating value is insufficient.
Such being the case, for instance, Japanese Patent Application Laid-Open Publication No. 60-79149 discloses a technology of utilizing the combustion heat of the combustion heater incorporated into the internal combustion engine for the purpose of speeding up warm-up of the engine and enhancing a performance of a car room interior warming device.
According to this technology, a high-temperature combustion gas of the combustion heater is introduced into an intake pipe of the internal combustion engine, and intake air of the engine is heated by this combustion gas, thereby facilitating actuation of the engine even when the internal combustion engine is in a low-temperature state.
The combustion gas emitted from the combustion heater is, however, an exhaust gas emitted when burning the fuel. The exhaust gas has a less oxygen content than an oxygen content in the air before being used for the combustion.
Therefore, as by the technology disclosed in the above Publication, when introducing the combustion gas into the intake pipe, if scheming to increase a ratio of the combustion gas contained in the intake air flowing through the intake pipe by augmenting the quantity of the combustion gas, though the warm-up of the engine is speeded up, a ratio of oxygen content in the intake air might decrease on the contrary.
As explained above, when the ratio of the oxygen content in the intake air decreases, a quantity of the combustion within the cylinders is restricted, resulting in such a state that the starting characteristic of the internal combustion engine might decline. The situation being so, if reducing the ratio of the combustion gas introduced into the intake pipe in order to ensure the oxygen quantity, this might in turn lead to an insufficient warm-up of the engine, and the starting characteristic is still impaired.
Especially at the engine starting time, since a crank shaft is rotated by an engine start assisting device such as a starter motor, etc., the engine speed is as low as, e.g., 100-200 rpm, and there is a small amount of intake air sucked into the cylinders from the atmospheric air via the intake pipe. Accordingly, there increases the ratio of the combustion gas in almost all intake air taken-in.
Therefore, the intake air containing the combustion gas at such a high ratio is absolutely unable to be used as engine intake air, and, in an extreme case, there is a possibility that the engine does not work.
It is a primary object of the present invention, which was devised under such circumstances, to provide an internal combustion engine having a combustion heater for raising a temperature of intake air of the internal combustion engine by introducing a combustion gas evolved when burning a fuel into the internal combustion engine and utilizing the heat held by the combustion gas, whereby a starting characteristic of the internal combustion engine is enhanced by positively replenishing oxygen to attain a sufficient oxygen content in the engine intake air while improving warm-up of the internal combustion engine.
To accomplish the above object, the present invention adopts the following means.
(1) An internal combustion engine having a combustion heater for raising a temperature of intake air of the internal combustion engine by utilizing combustion heat held by a combustion gas emitted when burning a fuel, and a combustion gas introducing passageway, through which a combustion gas discharge port of the combustion heater is connected to an engine intake passageway, for introducing the combustion gas into the intake passageway, comprising an oxygen supplying device for supplying oxygen to the engine intake air having become the intake air containing the combustion gas when the combustion gas is introduced via the combustion gas introducing passageway into the engine intake passageway, and an oxygen supply quantity control unit for controlling a quantity of oxygen supplied by the oxygen supplying device, and wherein the oxygen supply quantity control unit executes, at the engine starting time or before the engine starting time and also introducing the combustion gas into the engine intake passageway at that time, an augmentation control of augmenting the quantity of oxygen supplied to the engine intake air by the oxygen supplying device, the oxygen content in the engine intake air that is decreased due to the introduction of the combustion gas into the intake passageway, is supplemented under the augmentation control, and this supplement makes the engine intake air the intake air with oxygen content effective in enhancing a starting characteristic of the internal combustion engine.
Herein, what can be exemplified as xe2x80x9cthe oxygen supply quantity control unitxe2x80x9d may be an ECU (electronic control unit) serving as an engine control unit for controlling operations of the whole internal combustion engine. In this case, an optimum oxygen content corresponding to an operation state of the internal combustion engine can be supplied under the control by the ECU.
The term xe2x80x9cthe engine starting timexe2x80x9d implies a state where a crank shaft is rotated by an engine start assisting device such as, e.g., a starter motor or the like which is attached to the engine body, and a piston makes a reciprocating motion within the cylinder, namely in a cranking state, thereby the internal combustion engine eventually becomes independent enough to start its operation without depending on the starter motor.
The term xe2x80x9cbefore the engine starting timexe2x80x9d indicates the time before or preferably immediately before the engine (crank shaft) is rotated by the engine starting assisting device such as the starter motor, etc.
The term xe2x80x9cstarting characteristicxe2x80x9d is, as a matter of course, a condition of how the internal combustion engine works and implies how easily the internal combustion engine independently starts operating.
The term xe2x80x9cthe intake air with oxygen content effective in enhancing the starting characteristic of the internal combustion enginexe2x80x9d indicates a value obtained beforehand by a test performed for every internal combustion engine.
(2) The oxygen supplying device supplies the engine intake passageway with the oxygen through the combustion gas introducing passageway.
(3) The oxygen supplying device may be an air blow device capable of making an air quantity variable, and the air blow device may be an air blow fan for supplying the combustion heater with the air for combustion.
(4) The air blow fan includes a fan, a driving unit for rotationally driving the fan, and a fan rotational speed control device for controlling the rotational speed of the fan by controlling an operation of the driving unit. The fan rotational speed control device sets, at the engine starting time or before the engine starting time, the rotational speed of the fan higher than that in operation other than the starting time of the internal combustion engine. What can be exemplified as the fan rotational speed control device may be, e.g., the ECU serving as the engine control unit for controlling the whole internal combustion engine.
The term xe2x80x9cwhen in operation other than starting the internal combustion enginexe2x80x9d implies a state after the internal combustion engine has been started up, i.e., a state where, so to speak, the engine works. More specifically, that indicates a state in which the piston performs the reciprocating motion within the cylinder without depending upon the engine start assisting device such as the starter motor, etc., in other words, the piston is reciprocated by a combustion and explosion force gained at a combustion and explosion stroke in the operation strokes of the internal combustion engine, and the internal combustion engine operates independently of the engine start assisting device.
(5) A quantity of fuel supply to the combustion heater, at the engine starting time or before the engine starting time, is set equal to or smaller than the quantity of fuel supply when in the engine operation other than the engine starting time.
(6) The combustion heater includes an air supply passageway connected to the intake passageway and thereby functioning to supply the combustion heater with intake air as the air for combustion which flows through the intake passageway, and an intake air quantity regulating unit, provided between a connecting point at which the air supply passageway is connected to the intake passageway and a connecting point at which the combustion gas introducing passageway is connected to the intake passageway, for regulating a quantity of intake air in the intake passageway, and wherein the intake air quantity control unit, at the engine starting time or before the engine starting time and also introducing the combustion gas into the intake passageway at that time, may reduce the quantity of intake air.
Herein, for example, an intake throttle valve may be exemplified as xe2x80x9cthe intake air quantity regulating unitxe2x80x9d.
The term xe2x80x9creductionxe2x80x9d may embrace a case where the intake air quantity is 0 (zero). If the intake air quantity control unit is the intake throttle valve, the reduction of the intake air quantity implies closing the intake throttle valve, and the case where the intake air quantity is 0 (zero) implies that the intake throttle valve is fully closed.
(7) In the internal combustion engine of the present invention may further comprise a bypass passageway, bypassing cylinders and communicating the engine intake system with an engine exhaust system, and wherein the combustion gas may be, at the engine starting time or before the engine starting time and also discharging the combustion gas from the combustion heater at that time, flowed to an engine exhaust passageway from the intake passageway via the bypass passageway.
What can be exemplified as xe2x80x9cthe bypass passagewayxe2x80x9d may be a passageway extending from the combustion gas introducing passageway to the exhaust passageway and connected to the exhaust passageway at a point, in the vicinity of a catalyst converter provided in the exhaust passageway on the upstream side, of this exhaust passageway, and may be an EGR passageway constituting an EGR (Exhaust Gas Recirculation) device aiming at reducing production of oxides of nitrogen by restraining a rise in a combustion temperature by flowing the exhaust gas coming out of an exhaust port back to the intake side.
The present invention has the construction described above and therefor exhibits, for example, the following operational effects.
The oxygen supply quantity regulating unit performs, at the engine starting time or before the engine starting time and also introducing the combustion gas into the intake passageway at that time, the augmentation control of augmenting the quantity of oxygen supplied to the engine intake air by the oxygen supplying device. Then, an augmented oxygen content under this augmentation control is a quantity to supplement the oxygen content in the engine intake air, the oxygen content of which has been decreased due to the introduction of the combustion gas into the intake passageway, up to a quantity effective in enhancing the starting characteristic of the internal combustion engine.
Accordingly, even when the intake air containing the combustion gas flows as the engine intake air toward the cylinders of the internal combustion engine, the oxygen content enough to enhance the starting characteristic of the internal combustion engine, is ensured for the engine intake air at the engine starting time with a low rotational speed of the engine or before the engine starting time in a state where the engine does not yet rotate. Hence, even if the heater combustion gas defined as the exhaust gas is introduced into the intake passageway at the engine starting time or before the engine starting time, the starting characteristic of the internal combustion engine is good.
In addition, it is at the engine starting time or before the engine starting time and also introducing the combustion gas into the intake passageway at that time that the oxygen supply quantity control unit executes the augmentation control of augmenting the oxygen quantity, and therefore the combustion heater operates during the execution of the augmentation control. That is to say, the fuel is burned. Accordingly, a high-temperature combustion gas is introduced into the intake system at the engine starting time or before the engine starting time, and the temperature of the intake air is raised by this high-temperature combustion gas, thereby speeding up the warm-up of the engine.
Thus, in the internal combustion engine having the combustion heater according to the present invention, the combustion heater operates at the starting time of the internal combustion engine or before the engine starting time, and, in addition, the combustion gas in the state of increased oxygen content augmented by the oxygen supply quantity control unit is introduced into the engine intake air. Therefore, the warm-up characteristic can be enhanced, and the oxygen content in the engine intake air can be ensured with no deficiency. Hence, the starting characteristic of the engine at a low temperature is facilitated.
Further, in the case where the internal combustion engine is a diesel engine, an ignition method of the diesel engine is based on the heat of the compressed air, and therefore, if the combustion chamber takes a complicated configuration as seen in, e.g., a swirl chamber type diesel engine, a rate of a heat loss increases correspondingly. For this reason, there is a diesel engine adopting a low-temperature start assisting device such as a glow plug and an electric intake heater which emit the heat by flowing electric current through them when starting up and thus assist the ignition in the combustion chamber.
The present invention, when applied to the above-described diesel engine, makes it possible to eliminate the necessity for the low-temperature start assisting device because of being capable of starting at the low temperature as described above. It is therefore feasible to reduce the number of parts and downsize the internal combustion engine.
Moreover, according to the present invention, the engine can be started at the low temperature, and, as a result, for example, a rate of lowering the temperature of the combustion gas due to heat radiation in the engine intake system is small as compared to the internal combustion engine which is unable to start if not at a high temperature. Accordingly, there is no need for adopting, for instance, a special heat insulating material as a measure for preventing decreasing the heat radiation in the engine intake system.
Further, according to the present invention, the intake passageway is supplied with the oxygen via the combustion gas introducing passageway, so that the combustion gas introducing passageway may serve also as an oxygen supply member. This eliminates the necessity of, e.g., a pipe member used exclusively for supplying the oxygen, and consequently it is possible to reduce the number of parts and downsize the apparatus correspondingly.
Moreover, at the engine starting time or before the engine starting time and also introducing the combustion gas into the intake passageway at that time, the oxygen supply quantity control unit controls the air blowing device defined as the oxygen supply device, more specifically, the air blow fan to increase a quantity of oxygen flowing through the combustion gas introducing passageway, whereby the combustion gas containing a greater amount of oxygen can be sent to the intake passageway. Accordingly, as explained above, the starting characteristic of the internal combustion engine can be enhanced.
Furthermore, at the engine starting time or before the engine starting time, the fan rotational speed control unit properly sets the rotational speed of the fan higher than that of in operation other than the operation of starting the internal combustion engine, thereby making it feasible to ensure, for the engine intake air, the oxygen content enough to start up the internal combustion engine. Accordingly, even if the heater combustion gas, which is the exhaust gas, is introduced into the intake passageway at the engine starting time in which basically the engine speed is low or before the engine starting time in a state where the engine does not yet rotate, the internal combustion engine exhibits the preferable starting characteristic.
In addition, with the internal combustion engine, the lower the engine speed the less the intake air quantity. Hence, when the quantity of intake air is small, the quantity of fuel supplied to the combustion heater is reduced corresponding to this small quantity of intake air, in which case at least the combustion gas does not become rich.
According to the present invention, the quantity of intake air is increased from the engine starting time or before the engine starting time. Therefore, if the quantity of fuel supply to the combustion heater is set equal to or smaller than the fuel supply quantity which is made when in the operation other than the engine starting time, the combustion gas becomes lean.
Accordingly, at the engine starting time with the low engine speed or before the engine starting time in the state where the engine does not yet rotate, if the quantity of fuel supply to the combustion heater is set equal to or smaller than the fuel supply quantity when the engine works other than at least the engine starting time, whereby the lean combustion gas is introduced into the intake passageway. Consequently, the oxygen content in the engine intake air increases, and the starting characteristic of the internal combustion engine can be further enhanced.
At the engine starting time or before the engine starting time and also introducing the combustion gas into the intake passageway at that time, the intake air quantity regulating unit reduces the intake air quantity, in other words, if the intake throttle valve is applied to the intake air quantity regulating unit, it follows that the intake throttle valve is closed. Hence, in this case, even if the combustion gas discharged from the combustion heater is forced to flow back through the intake passageway, the back flow is hindered by the intake throttle valve.
Further, when the intake throttle valve is applied to the intake air quantity control unit, the intake throttle valve is provided at a portion, between a connecting point at which the air supply passageway is connected to the intake passageway and a connecting point at which the combustion gas introducing passageway is connected to the intake passageway, of the intake passageway. Therefore, it never occurs that the combustion gas enters the combustion heater via the air supply passageway from the connecting point disposed more upstream than the intake throttle valve, at which the air supply passageway is connected to the intake passageway. Accordingly, deterioration in combustion (a rich accidental fire) in the combustion heater can be prevented.
At the engine starting time or before the engine starting time and also introducing the combustion gas into the intake passageway at that time, the combustion gas flows through the bypass passageway which bypasses the cylinders, and escapes to the exhaust system from the intake system. Hence, a rise in pressure (exhaust pressure) in the intake system can be restrained. Consequently, the back flow can be prevented more effectively.
These together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.